1. Field of the Invention
The invention relates generally to battery-power distribution equipment and more particularly to RETMA rack chassis units that provide individually fused circuit branches for independent computer-data-network appliances at telco sites.
2. Description of the Prior Art
There is a growing need for competitive local exchange carriers to manage remote power control functions of internetworking devices at telephone company (telco) central offices. Competitive local exchange carriers (CLECs), incumbent local exchange carriers (ILECs), independent telephone companies, and other next generation service providers are now all offering a digital subscriber line (DSL) service that promises high-speed Internet access for both homes and businesses. DSL is expected to replace integrated services digital network (ISDN) equipment and lines, and DSL competes very well with the T1 line that has historically been provided by ILECS. A DSL drop costs about $40-60 per month, and is expected to quickly become the dominant subscriber-line technology.
The DSL service is provided by a switch that is co-located in a telco central office, i.e., a digital subscriber line access multiplexer (DSLAM). Many new competitive local exchange carriers are now deploying DSL service in several states. They are installing digital subscriber line access multiplexers in many locations. Such digital subscriber line access multiplexers are now available from a number of different manufacturers, e.g., Paradyne, Copper Mountain, Ascend, etc.
Nearly all such digital subscriber line access multiplexers are powered by 48-VDC battery power and all have operator console ports. And for emergencies, these DSLAMs usually have two independent 48-VDC battery power supplies, e.g., an A-channel and a B-channel. Most commercial DSLAMs are also controlled by large operating systems that host various application software. Unfortunately, this means most DSLAMs have the potential to fail or lock-up, e.g., due to some software bug.
When a digital subscriber line access multiplexer does lock-up, the time-honored method of recovering is to cycle the power, i.e., reboot. But when a digital subscriber line access multiplexer is located at a telco central office, such location practically prevents it being easy to reboot manually.
There are many large router and ATM switch farms around the country that are equipped by the leading vendors, e.g., Cisco, Bay Networks/Nortel, Ascend, Lucent, Fore, etc. So each of these too has the potential to lock-up and need rebooting, and each of these is very inconvenient to staff or visit for a manual reboot when needed.
Server Technology, Inc., (Sunnyvale, Calif.) markets a 48-VDC remote power manager and intelligent power distribution unit that provides for remote rebooting of remote digital subscriber line access multiplexers and other network equipment in telco central offices and router farms. The SENTRY 48-VDC is a network management center that eliminates the dispatching of field service technicians to cycle power and rectify locked-up digital subscriber line access multiplexers.
Statistics show that seventy percent, or more, of all network equipment lock-ups can be overcome by rebooting, e.g., cycling power off and on. A remote power controller, like the SENTRY, can reduce network outages from hours to minutes.
In a typical installation, the telco central office provides the competitive local exchange carriers with bare rack space and a 48-VDC power feed cable that can supply 60-100 amps. The single power input is conventionally distributed through a fuse panel to several digital subscriber line access multiplexers in a RETMA-type equipment rack. Individual fuses in such fuse panel are used to protect each DSLAM from power faults.
But such fuses frequently weld themselves to their sockets in the fuse panel due to loose contacts and high amperage currents. It is ironic therefore that many digital subscriber line access multiplexers do not have power on/off switches. Thus it requires the fuse to be pried out and put back in so the DSLAM can be powered-off for rebooting. But when the fuse is welded, removing the fuse without damaging the fuse panel can be nearly impossible.
The Server Technology SENTRY 48-VDC accepts from the telco or other site host an A-power feed cable and a B-power feed cable. Internally, DC-power is distributed to a set of xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d rear apron output terminal blocks that are protected by push-to-reset circuit breakers. The fuse panel is no longer required. The A-feed and B-feed are then matched to the newer digital subscriber line access multiplexers that also require A-power supply and B-power supply inputs.
Sometimes digital signaling lines can lose the carrier. In such cases, the respective DSLAM must be rebooted to restore the DS3 line. A technician is conventionally required to visit the DSLAM, and use a console port to monitor how the software reboots, and if communications are correctly restored to the DS3.
A SENTRY 48-VDC can be used to remotely power-off the digital subscriber line access multiplexer in the event the carrier is lost. A companion asynchronous communications switch can be used to establish a connection to the DSLAM""s console port. Power can be cycled to the DSLAM, and the asynchronous communications switch used to monitor the reboot operation to make certain that the carrier to the DS3 line is restored. The asynchronous communications switch is a low-cost alternative to the expensive terminal server typically used for console port access. The reboot process and the console port monitoring process can both be managed from an operations center, without the need to dispatch technical personnel to the remote location.
The floor space that a competitive local exchange carrier""s equipment rack sits upon is very expensive, so the equipment stuffed in the vertical space in a rack (xe2x80x9cU-spacexe2x80x9d) must be as compact as possible. A typical rack may house several digital subscriber line access multiplexers, a terminal server, a fuse panel, and 48-VDC modems. A SENTRY 48-VDC uses xe2x80x9c3Uxe2x80x9d (5.25 inches) of vertical RETMA-rack space, and combines the functions of a fuse panel, a terminal server, and a modem. As many as eight 20-amp devices, or four 35-amp devices can be supported.
Many host sites, and especially the telephone operating company offices, are very particular about the kind of equipment they allow on their premises. In general, equipment must meet the Network Equipment Building Standards (NEBS) established by Bellcore. For example, Bellcore has established the equipment specifications for fault-tolerance. NEBS was designed by Bellcore to manage and protect the large amount of intricate equipment located at telco central offices. NEBS specifications were designed to address every possible hazard that may occur at a telco central office, including fire, freeze and earthquake. NEBS certification requires products to be evaluated in extreme environments and phenomenon.
The importance and practice of collocating network servers at central offices has grown significantly in recent years with the growth of the ISP market and increasing opportunity for CLECs. NEBS certification is a necessity for equipment that is intended to be collocated within a telephone central office. A NEBS xe2x80x9cCertificate of Compliancexe2x80x9d can be obtained after product testing by MET Laboratories, and such certificate is recognized by all of the Regional Bell Operating Companies (RBOCs).
A consequence of NEBS is that equipment such as the SENTRY 48-VDC must have 48-VDC battery connectors that not only include positive and negative polarities, but ground too. Such connections must be made with double-hole battery compression lugs so that two nuts are used to fasten each cable. The ground connection must be made with a single cable which is at least one AWG size larger than the power feed cables to be able to carry the largest possible fault currents without open circuiting. The larger cable requires a larger compression lug size.
It is therefore an object of the present invention to provide a battery-power distribution panel for network appliances at a telco central office.
It is another object of the present invention to provide a battery-power distribution unit that eliminates the bulk of the individual cable wiring needed internally to feed power to eight or more network appliance loads.
Briefly, a battery-power distribution unit embodiment of the present invention comprises two printed circuit assembly bus units that carry eight pairs of xc2x1 screw terminal connections and their associated GMT-type fuses. Each A-side and B-side bus unit needs only one pair of heavy cables that feed it power inside a RETMA-rack cabinet. Heavy-duty foil buses etched on the printed circuit boards on both sides are reinforced with tinned copper flat bar to increase the current carrying capacity.
An advantage of the present invention is that a battery-power distribution unit is provided that is simple to manufacture and robust in operation.
Another advantage of the present invention is that a battery-power distribution unit is provided for a DSLAM power manager that is NEBS compliant.
These and many other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.